Hydrodesulfurization process



Aug. 4, 1953 w. A. HoRNE HYDRODESULFURIZATION PROCESS Filed Oct. 4, 1949@W Mwmmmu Zmruomnm ma mmwmm@ @REMO M OH W NH @dl mL O( iL M G N I l C .lN@ m w ,ON o A N R N P m QW m @@N @NN www @mw PGN @NN )@ON v0 00 :mwN@NN J MmmN T @M d @0N NNN @b mwN @0N @NN NNN NoN www NGN! CNN! @Q1 Wmv RR R R m u m 1 o 1 m A o 1 o o w w ww w v w v ww @n @n m 1 o A o. A o. Ao. A o. n c. o A o m N N N N N N N m N N N E N N N R R R R R `R R @TNIbw ENI @nl @Nn 10N @0N WANN WANN NHN WOW Ww/ .OOM @nw NN. .GN NmN Mw mw2mm L \M NNW mwmxwlmnmmww c@ NL www@ 00N NNN 00N 9N @NH @Q Q 4 0N NN gmO/N|\.I|f @AWN :Il ANW f. TQM MOH NNN -O A f` Il @NN @NN @mf Wwf A0YVlLLI/M f5- BORNE f1', ATTORNEY Patented Aug. 4, 1953HYDRODESULFURIZATION PROCESS William A. Horne, Oakmont, Pa., assignor toGulf Research & Development Company, Pittsburgh, Pa., a corporation ofDelaware Application October 4, 1949, Serial No. 119,513

4 Claims. (Cl. 196-26) This invention relates to a hydrodesulfurizationprocess and more particularly to a method of carrying outhydrodesulfurization Without undue consumption or" hydrogen.

The contact or adsorption hydrodesulfurization process has furnished therener of crude petroleum with one of the most eihcient methods ofremoving sulfur from sulfur-bearing charge stocks. As disclosed in U. S.applications Serial Nos. 699,671 and 699,672, led September 27, 1946, byW. A. Horne and J. F. Junge, now Patents 2,516,876-7, dated August 1,1950, this process consists in contacting a petroleum hydrocarbon andhydrogen-containing gas mixture in the presence of a contact agent suchas one comprising an iron group metal oxide such as nickel oxide on acarrier at an elevated temperature and pressure. During the course ofthe process nickel oxide is converted to nickel sulde thereby absorbingthe sulfur content of the petroleum hydrocarbon charge upon the contactagent. The process is continued until substantial amounts of hydrogensulde appear in the eiiluent at which time the process is stopped andthe contact agent regenerated to substantially its original form. Thisregeneration comprises an oxidation in which the nickel sulfide formedduring the hydrodesulfurization process is oxidized back to nickeloxide. Following the regeneration the system is repressured and onceagain put on-stream, although in some cases it may be desirable toprereduce the contact agent with a hydrogencontaining gas prior tointroducing the petroleum hydrocarbon charge.

Several diiiiculties have been encountered in the application of thistype process. Thus, the process as practiced prior to the presentinvention utilizes but approximately one-third to onehalf of the irongroup metal content of the contact agent as an absorption medium. As aconsequence, about one-third to one-half of the iron group metal contentis converted to iron group metal sulfide, whereas the remainder playsvirtually no part in the hydrodesulfurization.l Moreover, the greatpercentage of the iron group metal content that was converted to suldelies in the upstream or upper end of the hydrodesulfurization reactor,whereas the major portion of the unused contact lies in the downstreamor lower end of the reactor. During regeneration the iron group metalsulfide such as nickel sulfide in the upper part of the reactor isoxidized according to the following equation:

The SO2 so formed does not react with any NiS which it may encounter inthe contact bed, but reacts with the nickel or nickel oxide of theoriginal contact, or which is formed during the regeneration, int hefollowing manner:

Thus, a considerable portion of the nickel which has not becomeconverted into NiS during the onstream period is present as NiSOwA atthe end of the regeneration treatment. When this contact is again puton-stream or prereduced the NiSO4 will consume ve times as much hydrogenas does the ordinary NiO as shown in the following equations:

NiSO4-l-5H2 Ni|-4I+I2Ol-II2S NiO-l-HzNi-i-I-IzO This results in an undueconsumption of hydrogen without any economic gain being achieved.

In addition to the foregoing, there is the inefcient contact Waste dueto the fact that from one-half to two-thirds of the metal content of thecontact bed is not utilized. Thus a considerable portion of the contact(e. g., that portion not converted to NiS) will be reduced to the freemetallic state and thus will consume hydrogen without realizing anycorresponding economic gain. This free metallic portion of the bed willbe oxidized back to the oxide state during the course of theregeneration and thus will be continuously reduced and reoxidizedwithout serving its intended function as a sulfur absorbing agent. Forthese reasons it is highly desirable to operate the process so as toobtain as complete a sulfurization of the iron group metal content ofthe contact agent as is possible, consistent with the economics of theother process variables.

An object of the present invention is to re-duce the formation ofsulfates in an adsorption hydrodesulfurization contact bed,

Another object of the present invention is to provide a method wherebythe amount of hydrogen consumed in a hydrodesulfurization process ismaterially reduced.

A further object of this invention is to provide a method wherein a highpercentage of the metal [content of an adsorption hydrodesulfurizationprocess bed is utilized.

Further objects will appear hereinafter.

These and other objects are achieved by the process of the presentinvention which comprises passing petroleum hydrocarbons and ahydrogencontaining gas at an initial space velocity into a chambercontaining a contact agent selected from the group consisting of theiron group metals, iron group metal oxides, and mixtures thereofsupported on a carrier, reducing the space velocity during such passage,oxidatively regenerating said contact agent, and restoring it tosubstantially its original form, thereupon replacing the system onstreamby introducing hydrogen-containing gas and petroleum hydrocarbons intothe chamber.

The present application is similar to the aforementioned Horne and Jungeapplications as regards the operating conditions. The presentapplication is an advance over the above applications in that I havediscovered that by commencing with an initially relatively high spacevelocity and reducing the space velocity as the contact agent absorbsincreasing quantities of sulfur, the deleterious reactions involvingsulfate formation concomitant with the preferential sulfurization of theup-stream portion in a hydrodesulfurization contact bed reactor arevirtually eliminated. Depending upon the nature of the charge stock,temperature of reaction, and other process variables the initial,average and minimum space velocities will vary. Broadly, I have foundthat the initial space velocity may be from about 1 to 8 liquid volumesof charge per hour per volume of Contact agent. The final space velocityrange may be varied from about 1A?, to 2 volumes of charge per hour pervolume of contact agent. Within these ranges I have found rthat with lowboiling charge stocks such as those normally liquid petroleum fractionshaving an ASTM end point below 600 F., such as straight run or crackedgasolines and naphtha, an initial space velocity range of 4 to 8, and afinal space velocity range of 1 to 2 is to be preferred; For crude cils,and high boiling stocks in general, an initial space velocity of theorder of 1 to 4 Volumes of charge per hour, per volume contact agentshould be employed. This should be periodically or continuously reducedas the contact absorbs sulfur until a minimum space velocity of theorder of 0.25 to 1 volume of charge per hour, per volume of contactagent is achieved.

In addition to the foregoing effect on sulfate formation the applicationof my process permits a far greater percentage of sulfur absorption tobe achieved with a given size contact bed. This is due to the fact thata given unit of contact agent absorbs more sulfur during the on-streamcycle period than occurred in prior art processes.

The reaction takes place at varying temperatures, pressures and spacevelocities with the optimum conditions depending on the type chargestock that is used. For example, with low boiling hydrocarbons such asthose normally liquid petroleum fractions having an ASTM end point below600 F., such as straight run or cracked gasolines and naphtha, thetemperatures will usually lie between 600 and 800 F. I have found thatat temperatures below 600 F., the desulfurization activity of theContact diminishes whereas with temperatures higher than 800 F.excessive cracking reactions result in decreased product recovery andrapid coke formation which deactivates the contact. I have further foundthat the optimum pressures lie between 100 and 500 p. s. i. g. Atpressures below 100 p. s. i. g. the partial pressure of hydrogen is notsufficient to maintain desulfurization activity nor to suppress crackingreactions which result in coke formation. Increasing the pressure above500 p. s. i. g. results in only a slight incremental gain indesulfurization, and a decrease in the bromine number of the end productgasoline and is thus not commercially desirable.

This invention can be applied with exceptional success to high boilingpetroleum hydrocarbon oils such as total crude, topped crude or reducedcrude, i. e., petroleum oil resulting from removal of all or some of thestraight run fractions such as gas, gasoline, kerosene, naphtha, furnaceoil, gas oil, etc., which are normally removed from the above-definedtotal crude by the process of atmospheric and/or vacuum topping ordistillation. Charge stocks such as total crude which has been dilutedor admixed with lower boiling straight run or cracked petroleumfractions including gases are also included. Diluents of this kind maybe required in processing low gravity crudes such as some of those fromMississippi as well as those from Kuwait. Diluents may also be necessaryand preferred in desuliurizing topped or reduced crudes. The purpose ofthis diluent is to assist vaporization of the heavier constituents ofthe charge stock. In some cases it may be desirable to admix steam withthe charge stock to assist Vaporization. Preferred operating conditionsfor the aforementioned high boiling petroleum hydrocarbons may varywithin certain ranges depending upon the charge stock.

I have found the optimum temperature range to be from '750 to 950 forhigh boiling petroleum hydrocarbons. At temperatures below '.750" F. thedesuliurizing activity of the contact diminishes whereas at temperaturesgreater than 950 excessive cracking actions result in decreased productrecovery and rapid coke formation which deactivates the contact. havefurther ascertained the preferred pressure range to be between and 1000p. s. i. g. With pressures below 10G p. s. i. it appears that thepartial pressure of hydrogen is not sufficient to maintain desulfurizingactivity nor to suppress cracking reactions which result in cokeformation. Increasing the pressure above 1000 p. s. i. g. results inonly a slight incremental gain in desulfurization and isthus notcommercially desirable. I have found that best results are obtained witha hydrogen ratio to petroleum hydrocarbon of between 800 s. c. f/bbl. to20,000 s. c. f./bbl. or more. As disciosed in the aforementioned Horneand Junge applications the Contact may comprise a substantial amount ofan iron group metal oxide, i. e., nickel, iron or cobalt oxidessupported on a carrier, such as alumina. However, while the iron groupmetal oxides form the preferred contacts for my invention other contactagents may be utilized such as the elemental iron group metals, i. e.,nickel, iron, or cobalt; or mixtures of iron group metals and theiroxides, such as nickel-nickel oxide, iron-iron oxide, cobalt-cobaltoxide. As carriers I have found that any of the common substancesemployed for this purpose in the petroleum industry are applicable suchas kieselguhr, silica-gel, aluminum silicates, silica-alumina, Alfrax,Magnesol, Porocel, bauxite, diatomaceous earth, etc. Contact agents maybe prepared by any of the known methods such as single or multipleimpregnation, coprecipitation, adsorption from a colloidal solution,etc.

The present process is best understood by an examination of theaccompanying gure. The reactors shown in the accompanying ligure, namelyreactors Nos. I-VIII contain beds of contact agent which comprise, asindicated above,

a member of the group selected from the group consisting of the irongroup metals, iron group metal oxides, and mixtures thereof supported ona carrier. As will be explained hereinafter these reactors are atvarious stages of the process cycle such as being ori-stream, or in theregeneration stage. Accordingly, the chemical composition of thecontacts Will vary among the reactors since some of them will be more orless sulded in relation to the others.

A crude charge, such as a West Texas crude, enters the system throughline 0 passes through heater i2 into line H5. Hydrogen-containing gasenters the system through line |5, passes through heater I8 into line2Q. From line hl the crude charge passes through line 22, valve 24, line26, line 28 into reactor No. I. Since in the present example reactor Iis at the initial portion of its on-stream cycle the charge is passingthrough reactor I at a relatively high initial space velocity such as ofthe order of 2.0 volumes of charge per hour per volume of contact agent.The crude charge is accompanied into reactor No. I by thehydrogen-containing gas which has passed from line through line 30,valve 32 and line 28. In reactor No. I the crude charge ishydrodesulfurized and the sulfur contained therein is absorbed by thecontact material to form iron group metal sulde. Thehydrodesulfurization products are removed from reactor No. I by line 34and pass through line 35, valve 38 into line 40. From line 40 theproducts are removed from the system where they may undergo subsequentrening steps such as distillation, etc.

Were reactor No. I being regenerated, regeneration gas would enterreactor No. I after having passed through line 43, heater 53, line 52,line 3|, valve 33 and line 28. These regeneration gases after havingaccomplished the regeneration would be removed from reactor No. I byline line 35, valve 3?, line 30, from which they would enter line 66 andwould be removed from the sysn tem by means thereof.

For the purposes of the present example reactor No. II is in the latterstages of the regeneration cycle. rIhe regeneration treatment iseffected by regeneration gas entering the system through line d8 fromWhich it passes through heater 50, line 52, line '54, valve 56, line 58and line t5 through reactor No. 1I. This regeneration gas comprises anoxidative gas, that is, a gas such as oxygen or one containing oxygen,such as air. The regeneration gas products which include the sulfurformerly on the contact, but now in the form of sulfur dioxide, areremoved from reactor No. II by means of line 60 and pass through line62, valve 54, line G5 into line 5B from which they are removed from thesystem. rhe sulfur dioxide in this gas may be recovered in theconventional manner such as by ammonia absorption and stripping. Thesulfur dioxide free regeneration oir-gas may then serve to dilute theiirst regeneration gas admitted to the reactors. After regeneration iscomplete, which may readily be determined by the fact that the rate ofoxidation becomes quite small, the oxidizing gas is shut oir and thereactor steamed to remove any oxygen which may be present. Whereprereduotion is desired, valve 56 is then closed and hydrogen orhydrogen-containing gas is introduced into reactor No. II through valveIM so as to prereduce the contact bed. Where prereduction is notcontemplated, valve 58 as well as valve d4 may be opened following theaforementioned steam treatment and crude charge passed from line 10through line 12, line 46 and into reactor No. II along with the hydrogenfrom line 42. Were reactor No. II ori-stream, the crude charge andhydrogen mixture would be passing through reactor No. II in the mannerindicated above, and the hydrodesulfurization products would be removedby means of line 60, line 74, valve 16, line 'I3 and pass into line 5)Where they would be removed from the system.

In the present example reactor No. III is like wise assumed to be in theregenerative stage as is reactor No. II, although reactor No. III unlikereactor No. II is in the central rather than the latter portion of theregenerative cycle. Thus, regeneration gas is passing through reactorNo. III from line 52 by means of line 80, valve 52, line i, line andleaving reactor No, III by means of line 88, line 90, valve 92, line Siiinto line 65. Were reactor No. III on-stream, crude charge would beentering from line |4 by means of line 95, valve 95, line |00 and line5?. Hydrogen-containing gas would be entering reactor No. III from line20 through line |02, valve |013 and line 86. The hydrodesulfurizationproducts from reactor No. III would be leaving reactor No. III from line88, line |06, valve |08, line H0 from which they would pass into line 4Qand out of the system.

Reactor No. IV is at the early stage of the regenerative cycle. Thisportion of the cycle includes the depressuring and purging of thereactor such as by vacuum and/or with an inert substance such as steam(introduced by means of lines and valves not shown) so as to recover thevaluable hydrocarbons which remain in the contact bed. These valuablehydrocarbons and the inert substance are removed from reactor No. IV bymeans of line ||2 and pass through lines, valves and a condenser (notshown) so as to remove the inert substance after which the valuablehydrocarbons are passed into line H4, valve Ii, line ||8 and then intoline 40 from which they leave the system. Following the purge, oxidativeregenerative gas such as oxygen or an oxygen-containing gas such as airis introduced from line 52 through line |20, valve |22, line |24, line|26 into reactor No. IV. This regenerative gas leaves reactor No. IV bymeans of line H2, line |28, valve |30, and line |32 from Which it passesto line 56 and out of the system.

Were reactor No. IV ori-stream, crude charge Would pass from line I4through line |34, valve |36, line |38, line |26 into reactor No. IV, andthe hydrogen-containing gas would enter reactor No. IV through line |20,valve |42 and line |25.

Reactor No. V is in the last stage of the process cycle. Thus, in thepresent example utilizing a West Texas crude the space veloci-ty of thecharge through the reactor would be of the order oi' 0.5. The crudecharge is entering reactor No. V from line I4, through line |46, valve|45, line Hi8, and line |50. The hydrogen-containing gas is enteringreactor No. V from line 20 through line |52, valve |5fi and line |50.The hydrodesulfurization products are removed from reactor No. V bymeans of line |56, line |58, valve |60, and line |52 from which they arepassed to line @il and then out of the system. The termination of theOn-stream cycle Will vary With diierent charge stocks and differingreaction conditions.

In most cases the reaction Will be terminated when substantial amountsof hydrogen sulfide appear in the eiiiuent at the lowest space velocity.However, consideration should be given in many cases to the extent ofsulding of the contact and in these situations the process should becontinued until the contact has been substantially suliided to thedesired degree. I have found that in most cases it is desirable toachieve a sullding of the contact of the order of l to 90 per cent. Werereactor No. V being regenerated, regenera tion gas would be enteringreactor No. V from line 52 by means of line |64, valve |56, line |68 andline |55. The regeneration gas would be removed from reactor No. V bymeans of line |56, line H6, valve |l2, line |l4 from which it wouldenter line 36 and would be removed from the system by means thereof.

Reactor No. VI is on the latter half of the onstream cycle andaccordingly crude charge is entering reactor No. VI from line |4 bymeans or" line H6, valve |78, line |80 and line |82. Hydrogen-containinggas is entering reactor No. VI from line 25 by means of line |84, valve|86 and line |82. The space velocity of the charge should be of theorder of 0.5. The hydrodesulfurization products from reactor No. VI areremoved by means of line |88, line |95, valve |92, line |94, from whichthey enter line 4|] and are removed from the system. Were reactor No.VII being regenerated, regeneration gas would enter reactor No. VI fromline 52 by means of line ISF, valve |96, line 200 and line |32. Theseregeneration gases would be removed from reactor No. VI by means of line|88, line 202, valve 2513, line 255 from which they would enter line 65and would oe removed from the system by means thereof.

Reactor No. VII is in the central portion of the on-stream cycle and thecrude charge enters it from line |4 by means of line 208, valve 2|6.line 2|2 and line 2M. Hydrogen-containing gas is entering reactor No.VII from line 20 by means of line 2%6, valve 2|8 and line 2M. The spacevelocity of the charge through reactor No. VII should be of the order of1.0. The hydrodesulfurization products are removed from reactor No. VIIby means of line 220, line 222, valve 224, and line 225 from which theypass into line 46 and out of the system. Were reactor No. VII beingregenerated the regenerationv gas would enter reactor No. VII from line52 by means of line 225, valve 236, line 232 and line 2|4. Thisregeneration vgas would be removed from reactor No. VII by means of line226, line 234, valve 235, and line 238 from which it would enter line B6and thereby be removed from the system.

Reactor No. VIII is on the rst half of the onstream cycle. Accordingly,crude charge is entering reactor No. VIII from line I4 by means of line24U, valve 242, line 244 and line 246. Hydrogen-containing gas isentering reactor No. VIII from line 20 by means of line 248, valve 250and line 246. The space velocity of the charge through reactor No. VIIIshould be of the order of 1.5 I-Iydrodesulfurization products are beingremoved from reactor No. VIII by means of line 252, line 254, valve 256,and line 258 from which they enter line 40 and are removed from thesystem by means thereof. Were reactor No. VIII being regeneratedregeneration gas would enter reactor No. VIII from line 52 by means ofline 26e, valve 262, line 263, and line 246. The regeneration gas wouldbe removed from reactor No. VIII by means of line 252, line 253, Valve255, and line 251 and would enter line 66 from which it would be removedfrom the system.

The method of operation employed in the following example and in theaccompanying gure may be more fully understood by referring to thefollowing table which indicates the space velocity for each hour of runin each reactor, and the periodic reduction in space velocity as thecontact becomes increasingly sulded. Thus, the foregoing exampleembodied in the first hour of the run shown in the following table, i.e., reactor No. I had a space Velocity of 2.0 reactor Nos. II, III, IVwere in the regenerating stage of the cycle, reactor Nos. V and VI hadspace velocities of 0.5, reactor No. VII had a space Velocity of 1.0,and reactor No. VIII had a space velocity of 1.5. As the run progressesit will be seen from the table below that the space velocity in reactorNo. I decreases, and that reactor No. II goes from the regeneration tothe on-stream cycle, etc.

TABLE I Hourof Ruu l 2 3 4 5 6 7 8 Reactor No. SPACE VELOCITY I 2.0 1.51.0 0.5 0.5 R R R 2.0 1.5 1.0 0.5 0.5 R R R R 2.0 1.5 1.0 0.5 0.5 R R RR 2.0 1.5 1.0 0.5 0.5 0.5 R R R 2,0 1.5 1.0 0.5 0.5 0.5 R R R 2.0 1.51.0 1.0 0.5 0.5 R R R 2.0 1.5 1.5 1.0 0.5 0.5 R R 2.0

R= Regeneration.

Example I .--A West Texas crude charge having the inspection appearingbelow in Table II was hydrodesulfurized according to my method with acontact consisting of 22 per cent Ni as NiO on Houdry cracking catalystat a temperature of 850 F. and pressure of 500 p. s. i. g. The spacevelocity conditions were similar to those utilized in Table I. Theinspection of the crude charge and product appears in Table II.

TABLE II Hydrodesulfum'eation of West Temas crude inspection of chargeand typical liquid product Charge Product Gravity, API Distillaticn. "FI. B. P..

1 Carbon Residue, Bottom. PercentY Flasi OC "F B. W Sulfur, IeiV (BoSalt, iba/1.000 bbl The process of the present invention is not to beconstrued as limited to a system in which eight reactors are employed,since the foregoing description was given for illustrative purposessolely. Thus, a larger or smaller number of reactors may be utilized andthe space velocity employed during the on-stream portion of the cyclearranged so as to conform to the number of reactors in the system. Thispermits the process to be conducted in a continuous manner so that someof the reactors will be in the regenerative stage of the cyclewhile theother reactors are on-stream. If desired, the process'may be conductedin an intermittent manner such as with but one reactor or having all ofthe reactors simultaneously Von-stream or in regeneration. However, thecontinuous method of operation in which some reactors are on-stream,While others are in the regenerative phase, is to be considered thepreferred embodiment of my invention. Other process variables readilyapparent to one skilled in the art, such as the use of a single heaterfor the hydrogen-containing gas and the charge, etc., are also to beconsidered within the scope of my invention.

In the contact hydrodesulfurization reaction the charge stock willalways be at least partially in the vapor state but depending upon theboiling point of the specic charge stock and the physical conditions ofthe reaction the phase status may vary, Thus, in some instances thehydrodesulfurization reaction will be effected with the charge stocktotally in the vapor state, Whereas in other cases a mixed vapor-liquidphase will be utilized in the reaction.

The use of the present invention has the beneflcial effect of reducingsulfate formation in the Contact bed during regeneration. Through theprevention of this sulfate formation there is a material reduction inthe amount of hydrogen consumption during the on-stream or prereductioncycle following regeneration since the sulfate which would otherwise bepresent consumes five times as much hydrogen as does the normal oxideform. Furthermore, the utilization of this invention results in agreater degree of contact effectiveness being realized, i. e., anincreased percentage of absorption of sulfur compound on the contact iseffected during the on-stream cycle with a concomitant saving ofhydrogen, which otherwise would be expended in the reduction of theinitial oxide contact to the free metal contact.

In the following claims the expression oxidatively regenerating saidcontact agent and restoring it to substantially its original form is tobe understood as covering cases in which treatment with gases other thanoxidative gases are necessary to restore a contact to its original form.Thus, in the case of certain elemental metal or elemental metal-metaloxide contacts the prereduction treatment with hydrogen following theoxidative regeneration may prove desirable and this additional treatmentis to be construed as embodied in the following claims.

What I claim is:

1. The process for hydrodesulfurizing a petroleum hydrocarbon whichcomprises passing the petroleum hydrocarbon and a hydrogen containinggas into an enclosed chamber which contains a contact agent selectedfrom the group consisting of iron group metals, iron group metal oxidesand mixtures thereof, such passage taking place at an initial spacevelocity (volumes of charge per hour per volume of contact agent in theentire enclosed chamber), reacting sulfurous material in the petroleumhydrocarbon with the iron group portion of the contact agent to formiron group metal sulfide, reducing the space velocity (volume of chargeper hour per volume of contact agent in the entire enclosed chamber) tobelow the initial space velocity when a substantial amount of iron groupmetal sulfide has been formed, whereby the charge is in any givenportion of the contact agent a longer time than at 10 the initial spacevelocity, oxidatively regenerating the vcontactvagent to restoreitsubstantially to its original form and again placing the systemoli-stream by introducing hydrogen containing gas and petroleumhydrocarbon into the chamber.

2. The process for hydrodesulfurizing a petroleum hydrocarbon whichcomprises passing the petroleum hydrocarbon and a hydrogen containinggas into an enclosed chamber which contains a contact agent selectedfrom the group consistingfof iron group metals, iron group metal oxidesand mixtures thereof at an initial space velocity of between about l and8 liquid volumes of charge per hour per volume of contact agent in theentire enclosed chamber, reacting sulfurous material in the petroleumhydrocarbon with the iron group portion of the contact agent to formiron group metal sulfide, reducing the space velocity when a substantialamount of iron group metal sulde has been formed, to below the initialspace velocity and to between 0.25 and 2.0 liquid volumes of charge perhour per volume of contact agent in the entire enclosed chamber, wherebythe charge stock is in any given portion of the contact agent a longertime than at the initial space velocity, oxidatively regenerating thecontact agent to restore it substantially to its original form and againplacing the system on-stream by introducing hydrogen containing gas andthe petroleum hydrocarbon into the chamber.

3. The 'process for hydrodesulfurizing a high boiling petroleumhydrocarbon which comprises passing the high boiling petroleumhydrocarbon and a hydrogen containing gas into an enclosed chamber at atemperature between about 750 F. and 950 F. and a pressure of betweenabout and 1000 p. s. i., which chamber contains a contact agent selectedfrom the group consisting of iron group metals, iron group metal oxidesand mixtures thereof, such passage taking place at an initial spacevelocity (volumes of charge per hour per volume of contact agent in theentire enclosed chamber), reacting sulfurous material in the petroleumhydrocarbon with the iron group portion of the contact agent to formiron group metal sulfide, reducing the space velocity (volume of chargeper hour per volume of contact agent in the entire enclosed chamber) tobelow the initial space velocity when a substantial amount of iron groupmetal sulfide has been formed, whereby the charge is in any givenportion of the contact agent a longer time than at the initial spacevelocity, oxidatively regenerating the contact agent to restore itsubstantially to its original form and again placing the systemon-stream my introducing hydrogen containing gas and high boilingpetroleum hydrocarbon into the chamber.

4. The process for hydrodesulfurizing a high boiling petroleumhydrocarbon which comprises passing the high boiling petroleumhydrocarbon and a hydrogen containing gas into an enclosed chamber at atemperature between about 750 and 950 F. and pressure between about 100and 1000 p. s. i., which chamber contains a contact agent selected fromthe group consisting of iron group metals, iron group metal oxides andmixtures thereof, at an initial space velocity of between about l and 4liquid volumes of charge per hour per volume of contact agent in theentire enclosed chamber, reacting sulfurous material in the petroleumhydrocarbon with the iron group portion of the contact agent to formiron group metal sulfide, reducing the space velocity when a Substantialamount of iron group metal sulde of charge per hour per volume ofContact agent in 5 the entire enclosed chamber, whereby the charge stockis in any given portion of the Contact agent a longer time than at theinitial space velocity, oxidatively regenerating the contact agent torestore it substantially to its original form, again placing the systemori-stream by introducing hydrogen containing gas and the high boilinghydrocarbon into the chamber.

A. #I-IORNE.

References cited 1n the me of this patent UNITED sTATEs PATENTS NumberName Date Dormon Oct. 27, 1931 Gwynn Mar. 9, 1937 Lyman et al. Jan. A10,1939V Gwynn Oct; 31939 Szayna Feb. 17, 1942 Lovell Aug. 29, 1944Matuszak e June 19, 1945 Horne et a1 Aug. 1, 1950

1. THE PROCESS FOR HYDRODESULFURIZING A PETROLEUM HYDROCARBON WHICHCOMPRISES PASSING THE PETROLEUM HYDROCARBON AND A HYDROGEN CONTAININGGAS INTO AN ENCLOSED CHAMBER WHICH CONTAINS A CONTACT AGENT SELECTEDFROM THE GROUP CONSISTING OF IRON GROUP METALS, IRON GROUP METAL OXIDESAND MIXTURES THEREOF, SUCH PASSAGE TAKING PLACE AT AN INITIAL SPACEVELOCITY (VOLUMES OF CHARGE PER HOUR PER VOLUME OF CONTACT AGENT IN THEENTIRE ENCLOSED CHAMBER), REACTING SULFUROUS MATERIAL IN THE PETROLEUMHYDROCARBON WITH THE IRON GROUP PORTION OF THE CONTACT AGENT TO FORMIRON GROUP METAL SULFIDE, REDUCING THE SPACE VELOCITY (VOLUME OF CHARGEPER HOUR PER VOLUME OF CONTACT AGENT IN THE ENTIRE ENCLOSED CHAMBER) TOBELOW THE INITIAL SPACE VELOCITY WHEN A SUBSTANTIAL AMOUNT OF IRON GROUPMETAL SULFIDE HAS BEEN FORMED, WHEREBY THE CHARGE IS IN ANY GIVENPORTION OF THE CONTACT AGENT A LONGER TIME THAN AT THE INITIAL SPACEVELOCITY, OXIDATIVELY REGENERATING THE CONTACT AGENT TO RESTORE ITSUBSTANTIALLY TO ITS ORIGINAL FORM AND AGAIN PLACING THE SYSTEMON-STREAM BY INTRODUCING HYDROGEN CONTAINING GAS AND PETROLEUMHYDROCARBON INTO THE CHAMBER.